<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Billboard Trees Static Billboards</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import {OrbitControls} from 'three/addons/controls/OrbitControls.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  const fov = 75;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 1000;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.set(0, 2, 5);

  const controls = new OrbitControls(camera, canvas);
  controls.target.set(0, 2, 0);
  controls.minPolarAngle = 0;
  controls.maxPolarAngle = Math.PI / 2;
  controls.update();

  const scene = new THREE.Scene();

  function addLight(position) {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(...position);
    scene.add(light);
    scene.add(light.target);
  }
  addLight([-3, 1, 1]);
  addLight([ 2, 1, .5]);

  const trunkRadius = .2;
  const trunkHeight = 1;
  const trunkRadialSegments = 12;
  const trunkGeometry = new THREE.CylinderGeometry(
      trunkRadius, trunkRadius, trunkHeight, trunkRadialSegments);

  const topRadius = trunkRadius * 4;
  const topHeight = trunkHeight * 2;
  const topSegments = 12;
  const topGeometry = new THREE.ConeGeometry(
      topRadius, topHeight, topSegments);

  const trunkMaterial = new THREE.MeshPhongMaterial({color: 'brown'});
  const topMaterial = new THREE.MeshPhongMaterial({color: 'green'});

  function makeTree(x, z) {
    const root = new THREE.Object3D();
    const trunk = new THREE.Mesh(trunkGeometry, trunkMaterial);
    trunk.position.y = trunkHeight / 2;
    root.add(trunk);

    const top = new THREE.Mesh(topGeometry, topMaterial);
    top.position.y = trunkHeight + topHeight / 2;
    root.add(top);

    root.position.set(x, 0, z);
    scene.add(root);

    return root;
  }

  function frameArea(sizeToFitOnScreen, boxSize, boxCenter, camera) {
    const halfSizeToFitOnScreen = sizeToFitOnScreen * 0.5;
    const halfFovY = THREE.MathUtils.degToRad(camera.fov * .5);
    const distance = halfSizeToFitOnScreen / Math.tan(halfFovY);

    camera.position.copy(boxCenter);
    camera.position.z += distance;

    // pick some near and far values for the frustum that
    // will contain the box.
    camera.near = boxSize / 100;
    camera.far = boxSize * 100;

    camera.updateProjectionMatrix();
  }

  function makeSpriteTexture(textureSize, obj) {
    const rt = new THREE.WebGLRenderTarget(textureSize, textureSize);

    const aspect = 1;  // because the render target is square
    const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);

    scene.add(obj);

    // compute the box that contains obj
    const box = new THREE.Box3().setFromObject(obj);

    const boxSize = box.getSize(new THREE.Vector3());
    const boxCenter = box.getCenter(new THREE.Vector3());

    // set the camera to frame the box
    const fudge = 1.1;
    const size = Math.max(...boxSize.toArray()) * fudge;
    frameArea(size, size, boxCenter, camera);

    renderer.autoClear = false;
    renderer.setRenderTarget(rt);
    renderer.render(scene, camera);
    renderer.setRenderTarget(null);
    renderer.autoClear = true;

    scene.remove(obj);

    return {
      offset: boxCenter.multiplyScalar(fudge),
      scale: size,
      texture: rt.texture,
    };
  }

  // make billboard texture
  const tree = makeTree(0, 0);
  const facadeSize = 64;
  const treeSpriteInfo = makeSpriteTexture(facadeSize, tree);

  function makeSprite(spriteInfo, x, z) {
    const {texture, offset, scale} = spriteInfo;
    const mat = new THREE.SpriteMaterial({
      map: texture,
      transparent: true,
    });
    const sprite = new THREE.Sprite(mat);
    scene.add(sprite);
    sprite.position.set(
        offset.x + x,
        offset.y,
        offset.z + z);
    sprite.scale.set(scale, scale, scale);
  }

  for (let z = -50; z <= 50; z += 10) {
    for (let x = -50; x <= 50; x += 10) {
      makeSprite(treeSpriteInfo, x, z);
    }
  }

  scene.background = new THREE.Color('lightblue');

  {
    const size = 400;
    const geometry = new THREE.PlaneGeometry(size, size);
    const material = new THREE.MeshPhongMaterial({color: 'gray'});
    const mesh = new THREE.Mesh(geometry, material);
    mesh.rotation.x = Math.PI * -0.5;
    scene.add(mesh);
  }

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  function render() {
    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }

    renderer.render(scene, camera);

    requestAnimationFrame(render);
  }

  requestAnimationFrame(render);
}

main();
</script>
</html>

